Methods and apparatus for power conversion and data transmission in implantable sensors, stimulators, and actuators

ABSTRACT

Implantable devices and/or sensors can be wirelessly powered by controlling and propagating electromagnetic waves in a patient&#39;s tissue. Such implantable devices/sensors can be implanted at target locations in a patient, to stimulate areas such as the heart, brain, spinal cord, or muscle tissue, and/or to sense biological, physiological, chemical attributes of the blood, tissue, and other patient parameters. In some embodiments, the implantable devices can include power management schemes that have one or more AC-DC conversion chains arranged and configured to rectify the induced alternating current or voltage into one or more energy domains. Methods of use are also described.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.14/637,148, filed Mar. 3, 2015, now U.S. patent Ser. No. 10/004,913,which application claims the benefit of U.S. Provisional Application No.61/947,240, filed Mar. 3, 2014, titled “METHODS FOR POWER CONVERSION ANDDATA TRANSMISSION IN IMPLANTABLE SENSORS, STIMULATORS, AND ACTUATORS”,both of which are fully incorporated herein by reference.

INCORPORATION BY REFERENCE

All publications and patent applications mentioned in this specificationare herein incorporated by reference to the same extent as if eachindividual publication or patent application was specifically andindividually indicated to be incorporated by reference.

FIELD

This disclosure is related generally to wireless power transfer. Morespecifically, this disclosure relates to delivering wireless powerthrough tissue into a device implanted in a human or animal.

BACKGROUND

Current implanted electrostimulation systems typically include a largeimpulse generator including a titanium case enclosing the power sourceand circuitry used to generate the electrical pulses. Due to the largesize of these devices, the device itself is typically implanted within acavity in the body such as under the clavicle, below the rib cage, inthe lower abdominal region, or in the upper buttock. Electrical pulsesare then delivered to a targeted nerve or muscle region via leads routedunderneath the skin. Problems associated with this current approachinclude pocket infections, lead dislodgment, lead fracture orperforation, muscle tear due to implanting in or pulling out the leads,and limited locations for the placement of the electrodes.

The vast majority of wirelessly powered implantable devices operate inthe strongly coupled regime, e.g., inductive coupling. In conventionalwireless approaches using inductive coupling, the evanescent componentsoutside tissue (near the source) remain evanescent inside tissue whichdoes not allow for effective depth penetration of the wireless energy.Rectification techniques utilized for inductive coupling devices resultsin highly inefficient power conversion. For example, the rectificationefficiency can be as low as 5% using these techniques.

Many conventional implantable devices use a backscattered (BS) techniquefor data transmission due to its simplicity in implementation. However,this technique can be very sensitive to the heterogeneous nature of thetissue medium and the data rate is limited. Furthermore, the datatransmission performance can decay when implantable devices are placeddeep in the tissue. To solve this problem, an active transmitter may beimplemented but may consume substantial amount of power due tocomplexity in implementation.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features of the invention are set forth with particularity inthe claims that follow. A better understanding of the features andadvantages of the present invention will be obtained by reference to thefollowing detailed description that sets forth illustrative embodiments,in which the principles of the invention are utilized, and theaccompanying drawings of which:

FIG. 1 is a schematic diagram showing an external wireless powertransmitting module and one or more implanted modules configured toreceive wireless power.

FIG. 2 shows embodiments of a power conversion module that can beincluded in an implanted device that receives wireless power.

FIGS. 3A-3D illustrate various embodiments for implementing an AC-DCconversion chain in the power conversion module of FIG. 2.

FIGS. 4A-4C show an architecture of the regulator and compares with aconventional approach.

FIG. 5 compares the regulated voltage from this invention with that fromconventional approaches.

FIG. 6A-6E illustrate various embodiments for implementing an AC-DCconversion with regulator.

FIG. 7 shows one embodiment where various AC-DC conversion chains arecombined into a single chain powering multiple loads.

FIG. 8 shows an architecture for an implantable device including a datatransmitter and a power receiver.

FIG. 9 is an equivalent circuit for the data transmitter architecture ofFIG. 8.

FIG. 10 shows an architecture where the power receiver and datatransmitter share the same implant coupler.

FIGS. 11A-11B illustrate an output sequence of a data transmitter.

FIG. 12 is a schematic drawing of an external wireless powertransmitting module that includes a dual-band coupler structure.

SUMMARY OF THE DISCLOSURE

A wireless power receiving device is provided, comprising a couplerconfigured to induce an alternating current or voltage in the presenceof electromagnetic fields or oscillating sound pressure waves, a firstAC-DC conversion chain configured to rectify the induced alternatingcurrent or voltage into a first DC current or voltage in a first energydomain, a first DC load coupled to the first AC-DC conversion chain, asecond AC-DC conversion chain arranged in parallel with the first AC-DCconversion chain and configured to rectify the induced alternatingcurrent or voltage into a second DC current or voltage in a secondenergy domain, and a second DC load coupled to the second AC-DCconversion chain.

In some embodiments, the first or second AC-DC conversion chainscomprise a rectifier stage.

In one embodiment, the first or second AC-DC conversion chains comprisetwo or more rectifier stages.

In another embodiment, the first or second AC-DC conversion chainscomprise a rectifier stage in series with a DC-DC conversion circuit.

In one embodiment, the first or second AC-DC conversion chains comprisetwo or more rectifier stages in series with a DC-DC conversion circuit.

In another embodiment, the first or second AC-DC conversion chainscomprise a rectifier stage in parallel with a capacitor and a DC-DCconversion circuit, with a battery connected to an output of the DC-DCconversion circuit.

In an additional embodiment, the first or second AC-DC conversion chainscomprise two or more rectifier stages in parallel with a capacitor and aDC-DC conversion circuit, with a battery connected to an output of theDC-DC conversion circuit.

In some embodiments, the first or second AC-DC conversion chainscomprise a rectifier stage in series with a DC-DC conversion circuit anda battery.

In one embodiment, the first or second AC-DC conversion chains comprisetwo or more rectifier stages in series with a DC-DC conversion circuitand a battery.

In some embodiments, the first or second AC-DC conversion chainscomprise a rectifier stage in series with a DC-DC conversion circuit, abattery, and a second DC-DC conversion circuit.

In other embodiments, the first or second AC-DC conversion chainscomprise two or more rectifier stages in series with a DC-DC conversioncircuit, a battery, and a second DC-DC conversion circuit.

In one embodiment, the first DC current or voltage in the first energydomain is optimized for the first DC load.

In some embodiments, the second DC current or voltage in the firstenergy domain is optimized for the second DC load.

In other embodiments, the first energy domain comprises a low-voltagedomain.

In an extra embodiment, the first DC load comprises sensor circuitry,digital logic, a data transceiver, an analog oscillator, or an analogclock.

In some embodiments, the second energy domain comprises a high-voltagedomain.

In other embodiments, the second DC load comprises a battery, astimulator, or an actuator.

A wireless power system is also provided, comprising an external powertransmitting module configured to manipulate evanescent fields tocontrol propagating fields inside tissue generating a spatially focusingand adaptive steering field inside tissue, and an implantable moduleconfigured to receive wireless power from the external powertransmitting module via the spatially focusing and adaptive steeringfield, the implantable module including a coupler configured to inducean alternating current or voltage in the presence of electromagneticfields or oscillating sound pressure waves, a first AC-DC conversionchain configured to rectify the induced alternating current or voltageinto a first DC current or voltage in a first energy domain, a first DCload coupled to the first AC-DC conversion chain, a second AC-DCconversion chain arranged in parallel with the first AC-DC conversionchain and configured to rectify the induced alternating current orvoltage into a second DC current or voltage in a second energy domain,and a second DC load coupled to the second AC-DC conversion chain.

A wireless power receiving device is further provided, comprising acoupler configured to induce an alternating current or voltage in thepresence of electromagnetic fields or oscillating sound pressure waves,an AC-DC conversion chain comprising a rectifier stage in series with aDC-DC conversion circuit, the AC-DC conversion chain being configured torectify the induced alternating current or voltage into a DC current orvoltage, and a DC load coupled to the AC-DC conversion chain.

A wireless power receiving device is also provided, comprising a couplerconfigured to induce an alternating current or voltage in the presenceof electromagnetic fields or oscillating sound pressure waves, an AC-DCconversion chain comprising two or more rectifier stages in series witha DC-DC conversion circuit, with a battery connected to an output of theDC-DC conversion circuit, the AC-DC conversion chain being configured torectify the induced alternating current or voltage into a DC current orvoltage, and a DC load coupled to the AC-DC conversion chain.

A wireless power receiving device is provided, comprising a couplerconfigured to induce an alternating current or voltage in the presenceof electromagnetic fields or oscillating sound pressure waves, an AC-DCconversion chain comprising a rectifier stage in parallel with acapacitor and a DC-DC conversion circuit, with a battery connected to anoutput of the DC-DC conversion circuit, the AC-DC conversion chain beingconfigured to rectify the induced alternating current or voltage into aDC current or voltage, and a DC load coupled to the AC-DC conversionchain.

A wireless power receiving device is further provided, comprising acoupler configured to induce an alternating current or voltage in thepresence of electromagnetic fields or oscillating sound pressure waves,an AC-DC conversion chain comprising two or more rectifier stages inparallel with a capacitor and a DC-DC conversion circuit, with a batteryconnected to an output of the DC-DC conversion circuit, the AC-DCconversion chain being configured to rectify the induced alternatingcurrent or voltage into a DC current or voltage, and a DC load coupledto the AC-DC conversion chain.

A wireless power receiving device is also provided, comprising a couplerconfigured to induce an alternating current or voltage in the presenceof electromagnetic fields or oscillating sound pressure waves, an AC-DCconversion chain comprising a rectifier stage in series with a DC-DCconversion circuit and a battery, the AC-DC conversion chain beingconfigured to rectify the induced alternating current or voltage into aDC current or voltage, and a DC load coupled to the AC-DC conversionchain.

A wireless power receiving device is further provided, comprising acoupler configured to induce an alternating current or voltage in thepresence of electromagnetic fields or oscillating sound pressure waves,an AC-DC conversion chain comprising two or more rectifier stages inseries with a DC-DC conversion circuit and a battery, the AC-DCconversion chain being configured to rectify the induced alternatingcurrent or voltage into a DC current or voltage, and a DC load coupledto the AC-DC conversion chain.

A wireless power receiving device is provided, comprising a couplerconfigured to induce an alternating current or voltage in the presenceof electromagnetic fields or oscillating sound pressure waves, an AC-DCconversion chain comprising a rectifier stage in series with a DC-DCconversion circuit, a battery, and a second DC-DC conversion circuit,the AC-DC conversion chain being configured to rectify the inducedalternating current or voltage into a DC current or voltage, and a DCload coupled to the AC-DC conversion chain.

DETAILED DESCRIPTION

Implantable devices/sensors can be wirelessly powered by controllingpropagating electromagnetic waves in tissue. The implantable devices canbe implanted in humans or in other animals such as pets, livestock, orlaboratory animals such as mice, rats, and other rodents. Suchimplantable devices/sensors can be implanted at target locations in apatient, as non-limiting examples, to stimulate areas such as the heart,and/or to sense biological, physiological, chemical attributes of theblood, tissue, and other patient aspects. Difficulties in achievingwireless power transfer can occur in the mismatch between the size ofthe implantable devices/sensors and the power transfer source, the depthof the devices/sensors in a patient, and additionally the spatialarrangement (for example, displacement and orientation) of thedevices/sensors relative to the power transfer source.

Certain embodiments of the present disclosure are directed tomanipulation of evanescent fields outside a patient's tissue withsub-wavelength structures to excite/control propagating fields inside apatient's tissue and thereby generate a spatially focusing and adaptivesteering field/signal in the tissue. A sub-wavelength structuregenerates fields that are evanescent in nature near the source.

This disclosure provides embodiments of sub-wavelength structures andmethods for controlling the excitation of those structures to excite thepropagating modes inside tissue from the evanescent modes outsidetissue. As a result, this approach is very effective in transportingenergy to absorption-limited depth inside tissue. The designs disclosedherein include structures that use tissue as a dielectric waveguide totunnel energy into the body. The energy can be received by an implantedmodule which will be discussed below, to allow for wireless powertransfer to tiny implanted devices (millimeter or smaller in scale) atdepths unattainable with conventional inductive coupling technology.

This disclosure provides a midfield wireless powering approach thatintegrates an external module configured to transmit wireless power, andone or more implanted modules configured to receive wireless power thatcombines an impulse generator and at least one stimulation electrodetogether into a small, leadless, implantable device. In someembodiments, the implanted module can be small enough to be deliveredvia a catheter or a hypodermic needle. For example, the implanted modulecan be as small as a few millimeters in diameter (2-3 mm) down to havingdiameters on the order of 100's of microns or less. The external andimplant modules allow for the transfer of wireless power to nearly anylocation in the body at performance levels far exceeding requirementsfor both complex electronics and physiological stimulation. Because theimplanted modules are small, they can be injected into the targetednerve or muscle region directly without the need for leads andextensions, to provide sensing and stimulation to the targeted nerve,muscle, or tissue region. When the implantable devices are wirelesslypowered by electromagnetic fields, power can be focused within humantissue in the electromagnetic midfield using frequencies betweenapproximately 400 MHz and 2.5 GHz. This allows for much smaller devicesthat can be injected deep in the tissue using a catheter or a needle.Further details on the implanted and external modules described hereincan be found in International Application No. PCT/US2014/055885, filedSep. 16, 2014, incorporated herein by reference.

This disclosure provides methods to increase the efficiency ofrectification and power management of wirelessly powered implantabledevices that are operated in a weakly coupled regime using midfieldwireless powering approach. With this approach, the transmission ofelectromagnetic fields or oscillating sound pressure waves from theexternal module to the implantable device(s) is very low, ranging fromtens to hundreds of millivolts. Rectification techniques present in thisdisclosure, can be as high as 50%.

This disclosure further provides methods and apparatus for datatransmission to and from the implantable device(s) to the externalmodule that works in a heterogeneous tissue medium, consumes minimalpower, and supports a high data rate.

FIG. 1 is a schematic figure showing an external wireless powertransmitting module 102 external to a patient and one or moreimplantable modules 104 disposed within the patient. The externalwireless power transmitting module can include one or moresub-wavelength structures 106 configured to manipulate evanescent fieldsoutside a patient's tissue to excite/control propagating fields inside apatient's tissue to generate a spatially focusing and adaptive steeringfield/signal in the tissue. The one or more implanted modules areconfigured to receive wireless power from the external module. Theimplanted modules can optionally include features for sensing and/orstimulating tissue, such as an electrode. Because the power levelssupported by a midfield wireless powering approach far exceedrequirements for microelectronic technologies, more sophisticatedfunctions can be implemented such as real-time monitoring of chronicdisease states or closed-loop biological sensing and control by theimplanted module.

FIG. 2 shows embodiments of a power conversion module 208 that can beincluded in the implantable module of FIG. 1. The power conversionmodule 208 can include one or more AC-to-DC conversion chains 210arranged in parallel. Each chain 210 can be configured to rectify thealternating current/voltage (AC) induced by the electromagnetic fieldsor oscillating sound pressure waves and received by the implantedmodules into direct current/voltage (DC), supplying energy to one ormore loads on the implanted device. Since the implanted modulesdescribed herein can be fully customized with many different loads, thechains can rectify energy to loads comprising any sensor, stimulator,actuator, data transmitter, data receiver, digital controller, or anyother module in or on the implantable device that must be powered by thewireless power signal. The parallel configuration of AC-to-DC conversionchains 210 in FIG. 2 can isolate noise from different loads and improvethe overall conversion efficiency across voltage and energy domains(e.g., low and high voltage/energy domains).

FIGS. 3A-3D illustrate various embodiments for implementing each of theAC-DC conversion chains of FIG. 2. FIG. 3A shows an AC-DC conversionchain 310 comprising a single rectifier stage 312. The output voltageusing this implementation can be low, ranging from tens to hundreds ofmillivolts. FIG. 3B shows an AC-DC conversion chain 310 comprising twoor more rectifier stages 312 placed in series to increase the outputvoltage. With multiple rectifiers in series, power is dissipated to therectifier. Hence, using more than one rectifier stage to attain a highoutput voltage can incur significant energy loss to the rectificationchain, resulting in low conversion efficiency.

One way for increasing the efficiency of a power rectification circuitis to use DC-DC converters in conjunction with one or more rectifierstages. Thus, FIG. 3C illustrates an AC-DC conversion chain 310comprising a single rectifier stage 312 in series with a DC-DC converter314, and FIG. 3D shows an AC-DC conversion chain 310 comprising two ormore rectifier stages 312 in series with a DC-DC converter 314. In FIGS.3C-3D, one or more rectifier stages 312 can be used to rectify the ACvoltage received by the implanted module to a low DC voltage that drivesthe DC-DC conversion circuits. The DC-DC conversion circuits can thenconvert the low DC voltage to a high DC voltage to provide power to theconnected load. In some embodiments, the DC-DC conversion circuits mayoperate at a frequency lower than the power transmission frequency, andmay operate at an efficiency that is much higher than the rectificationcircuit. Since the controlling circuitry for the DC-DC conversioncircuits is powered by the rectified DC voltage, the DC-DC conversioncircuits are isolated from the AC voltage. In this scenario, the overallconversion efficiency for an output voltage of 4 V may be as high as50%, whereas rectification to the same voltage in embodiments FIGS. 3Aand 3B may be as low as 25% in the same scenario with the same receivedAC power.

FIGS. 4A and 4C show architectures of a regulator and are compared witha conventional approach as seen in FIG. 4B. FIGS. 4A and 4C show anAC-DC conversion chain 410 including a battery 416 to maintain a stableoutput voltage. FIG. 4B, in contrast, shows a feedback loop forregulators where an internally generated voltage from a circuit such asa bandgap reference is used to regulate the voltage to the referencevalue. Power above this reference value is drained to the energy sinkand is dissipated.

FIG. 4A is a high level schematic drawing of the circuit shown in FIG.4C. In the embodiment of FIG. 4C, a battery 416 a can be used as both avoltage reference and power leveler. Many sensor circuits require alevel voltage in order to maintain calibration and reduce sensor noise.Battery chemistries allow the battery to maintain a stable voltage sincethey are non-linear with stored charge, and the voltage is dependent onelectro-chemical properties of the battery cell. When the battery isconnected to the output of DC-DC converter 414, it stabilizes the inputvoltage of the DC-DC converter in conjunction with a capacitor 418. Thebattery acts as an energy source for negative fluctuations in voltage,an energy storage device for positive fluctuations in voltage, and avoltage reference for deriving the operating point of the input node.Hence, the circuits of FIGS. 4A and 4C operate like a voltage regulator.

FIG. 5 compares the regulated voltage from the embodiment of FIGS. 4Aand 4C with that from conventional approaches. The regulated voltage 520using the conventional approaches is the lowest bound of the unregulatedvoltage 522. In the disclosed embodiment, the regulated voltage 524according to this disclosure yields the average of the unregulatedvoltage. So the disclosed embodiment is more efficient than conventionalapproaches.

FIGS. 6A-6E show a variation of the embodiment of FIGS. 4A and 4C. InFIG. 6A, the single stage rectifier of an AC-DC conversion chain 610 isreplaced by two or more rectifier stages 612, which can be connected tothe DC-DC converter 614 and battery 616 as shown. In FIGS. 6B and 6C,output of the battery 616 can be used to power the loads. The embodimentof FIG. 6B includes a single rectifier stage 612, and the embodiment ofFIG. 6C includes more than one rectifier stage 612 along with the DC-DCconverter 614 and battery 616. For some loads, the required voltage canbe lower than the output voltage of the battery, for example loads withsensor or digital logic circuits. In these cases, an additional DC-DCconverter 626 is used to convert the high DC voltage from the battery616 to a low DC voltage for the load, as shown in FIGS. 6D and 6E.

The AC-DC conversion chains shown in FIGS. 3A-3D and 6A-6E can also becombined into a single chain powering up multiple loads as shown in FIG.7. This can potentially save some components in the implementation. Forexample, in FIG. 7, a first load 728 can be connected to a singlerectifier stage 712 (e.g., the conversion chain of FIG. 3A), a secondload 730 can be connected to a single rectifier stage 712 in series witha DC-DC conversion circuit 714 (e.g., the conversion chain of FIG. 3C),a third load 732 can be connected to a single rectifier stage 712 inseries with a DC-DC conversion circuit 714 and a battery 716 (e.g., theconversion chain of FIG. 6B), and a fourth load 734 can be connected toa rectifier stage 712 in series with a DC-DC conversion circuit 714, abattery 716, and a second DC-DC conversion circuit 726 (e.g., theconversion chain of FIG. 6D). It can be understood that othercombinations of the conversion chains of FIGS. 3A-3D and 6A-6E can beimplemented to power a plurality of loads connected to the implantedmodule.

Each parallel chain in FIG. 2 can be configured to yield a differentoutput voltage that is optimized for a particular load on the implantedmodule. This parallel architecture can divide the circuit intolow-voltage and high-voltage domains. For example, the low-voltagedomain can be used to power digital circuitries in the sub-thresholdregion to minimize power consumption. The high-voltage domain can beused to charge up a battery of the implanted module and to powerstimulation and/or actuation circuitries, which in general require highoperating voltage.

Another aspect of this disclosure is a data transmitter of a wirelesslypowered implanted module (such as the implanted module 104 from FIG. 1).FIG. 8 illustrates an architecture for an implantable module or device804, containing a power receiver 836, e.g., AC-DC conversion chain 810,and a data transmitter 838, including pulse generator 840. Energy forthe functioning of the data transmitter can come from the powerreceiver, by harvesting power from the incident electromagnetic fieldswith the implant coupler 842.

FIG. 9 illustrates the equivalent circuit model of a data transmitter938 similar to the embodiment shown in FIG. 8, including pulse generator940. Leveraging on the inductive property of the implant coupler 942(Lant, Rant) and wirebonds 944 from the coupler to the on-chip pads(Lwb, Rwb), they form a bandpass filter when in conjunction with anon-chip capacitor 946 (Cchip). That is, the implant coupler, wirebonds,and on-chip pads are part of the transmitter chain.

The power receiver and data transmitter of FIG. 8 can share the sameimplant coupler 1042 as shown in FIG. 10. This can be implemented with atransmit-receive switch 1048 (T/R switch), which can connect the AC-DCconversion chain 1010 and the pulse generator 1040 to a single implantcoupler 1042.

Input to the pulse generator of FIGS. 8-9 can be a sequence of binarysymbols, and the output can be a sequence of pulses, as shown in FIGS.11A-11B. Due to the bandpass filtering, the radio-frequency (RF) signalshown in FIGS. 11A-11B is widened and may have some ringing. Datasymbols can be encoded into the RF signal as on-off keying shown in FIG.11A or amplitude shift keying shown in FIG. 11B.

The pulse width Tpulse can be chosen to be such smaller than the symbolperiod T such that the peak power (power over the period Tpulse) is muchlarger than the average power (power over the period T). This will yielda high data rate from a few kbps to 100 Mbps while the average powerconsumption is low, for example, 10 μW average power with 10 mW peakpower. Tissue composition and structure have less impact on the pulsedRF modulation than backscattered modulation. Furthermore, the use of thecoupler and the wirebonds as part of the transmitter reduces complexity.

To support simultaneous power delivery and data receiving at theexternal power transmitting module (e.g., external module 102 from FIG.1), a vast number of conventional implantable systems use separatefrequencies for the power and data carriers, and use separate couplerstructures optimized to the respective carriers. The inclusion of twocoupler structures increases the size of the external module. Thisdisclosure provides methods and apparatus to combine the two couplerstructures into one, enhancing the compactness of the external module.

FIG. 12 shows a schematic of the external wireless power transmittingmodule 1202 having a dual-band coupler structure 1250 to combine twocoupler structures into one. The band around frequency f₁ from RF powersource 1252 can be used to transmit power to the implantable module(e.g., the implantable module of FIG. 1). The dual-band couplerstructure can be configured to manipulate evanescent fields outside apatient's tissue to excite/control propagating fields inside a patient'stissue. The band around frequency f₂ at LO 1254 can be used to receivedata from the implantable module. In one embodiment, the power carrieruses 1.6 GHz while the data carrier uses 2.4 GHz. A circulator 1256 canbe included to separate the two signals into two paths. The upper pathcan be used to transmit power to the implantable module while the lowerpath can be used to decode data receiving from the implantable module.

The upper path of FIG. 12 can include an RF power source, a mixer, and apower amplifier (PA). The frequency of the RF power source is f₁. Thepower carrier can also carry data to the implantable module.

The lower path of FIG. 12 can include a notch filter, a low-noiseamplifier (LNA), a mixer, a local oscillator, and a datademodulator/decoder. The output frequency of the oscillator is f₂. Theperformance of the circulator in isolating signals to the upper andlower paths is very sensitive to the degree of impedance matching of thecoupler to the surrounding tissue medium. It is difficult to achieveperfect matching due to the variability of patient tissue structure andlocation of the implantable module. A notch filter can be included toreduce the leakage signal from the upper path. The filtered signal canthen be amplified by the LNA, and followed by down conversion tobaseband signals for data demodulation and decoding. In some embodimentsof the invention, the notch filter can be integrated with the LNA, andin another embodiment, the LNA can precede the notch filter.

While the present disclosure is amenable to various modifications andalternative forms, specifics thereof have been shown by way of examplein the drawings and will be described in further detail. It should beunderstood that the intention is not to limit the disclosure to theparticular embodiments and/or applications described. Methods of usingthe embodiments described herein are also included. Various embodimentsdescribed above and shown in the figures and attachments may beimplemented together and/or in other manners. One or more of the itemsdepicted in the drawings/figures can also be implemented in a moreseparated or integrated manner, as is useful in accordance withparticular applications.

What is claimed is:
 1. A wireless power system, comprising: an externalpower transmitting module configured to manipulate evanescent fields tocontrol propagating fields inside tissue generating a spatially focusingand adaptive steering field inside tissue; and an implantable moduleconfigured to receive wireless power from the external powertransmitting module via the spatially focusing and adaptive steeringfield, the implantable module including: a coupler configured to inducean alternating current or voltage in the presence of electromagneticfields or oscillating sound pressure waves; a first AC-DC conversionchain configured to rectify the induced alternating current or voltageinto a first DC current or voltage in a first energy domain; a first DCload coupled to the first AC-DC conversion chain; a second AC-DCconversion chain arranged in parallel with the first AC-DC conversionchain and configured to rectify the induced alternating current orvoltage into a second DC current or voltage in a second energy domain;and a second DC load coupled to the second AC-DC conversion chain. 2.The device of claim 1, wherein the first or second AC-DC conversionchains comprise a rectifier stage.
 3. The device of claim 1, wherein thefirst or second AC-DC conversion chains comprise two or more rectifierstages.
 4. The device of claim 1, wherein the first or second AC-DCconversion chains comprise a rectifier stage in series with a DC-DCconversion circuit.
 5. The device of claim 1, wherein the first orsecond AC-DC conversion chains comprise two or more rectifier stages inseries with a DC-DC conversion circuit.
 6. The device of claim 1,wherein the first or second AC-DC conversion chains comprise a rectifierstage in parallel with a capacitor and a DC-DC conversion circuit, witha battery connected to an output of the DC-DC conversion circuit.
 7. Thedevice of claim 1, wherein the first or second AC-DC conversion chainscomprise two or more rectifier stages in parallel with a capacitor and aDC-DC conversion circuit, with a battery connected to an output of theDC-DC conversion circuit.
 8. The device of claim 1, wherein the first orsecond AC-DC conversion chains comprise a rectifier stage in series witha DC-DC conversion circuit and a battery.
 9. The device of claim 1,wherein the first or second AC-DC conversion chains comprise two or morerectifier stages in series with a DC-DC conversion circuit and abattery.
 10. The device of claim 1, wherein the first or second AC-DCconversion chains comprise a rectifier stage in series with a DC-DCconversion circuit, a battery, and a second DC-DC conversion circuit.11. The device of claim 1, wherein the first or second AC-DC conversionchains comprise two or more rectifier stages in series with a DC-DCconversion circuit, a battery, and a second DC-DC conversion circuit.12. The device of claim 1, wherein the first DC current or voltage inthe first energy domain is optimized for the first DC load.
 13. Thedevice of claim 12, wherein the second DC current or voltage in thefirst energy domain is optimized for the second DC load.
 14. The deviceof claim 13, wherein the first energy domain comprises a low-voltagedomain.
 15. The device of claim 13, wherein the first DC load comprisessensor circuitry, digital logic, a data transceiver, an analogoscillator, or an analog clock.
 16. The device of claim 14, wherein thesecond energy domain comprises a high-voltage domain.
 17. The device ofclaim 15, wherein the second DC load comprises a battery, a stimulator,or an actuator.